Ground Penetrating Radar Results Anyone Can Understand

A buried utility line is struck about once every six minutes, according to the Common Ground Alliance. That statistic should worry any jobsite manager who needs to trench or excavate. It was one of the inspirations behind Leica DSX, a new ground penetrating radar solution from Hexagon AB that seems poised to change how contractors detect underground utilities.

Ground penetrating radar (GPR) was patented in 1910 and first used for archeological and scientific applications. A commercial GPR system debuted about 50 years ago. But even today’s GPR systems are difficult and time-consuming to use. You need to dedicate a day to mapping the ground on-site, then one or two additional days back in the office to perform data analysis and interpret the resulting radargram.

This isn’t something just anyone can do. Accurately interpreting a radargram takes a lot of training and experience. So rather than owning a GPR system and keeping a technician on staff, construction firms are much more likely to contract with a utility locating vendor for each utility surveying job. That is not only expensive but slow. And it adds a scheduling dependency to the project.

That’s why the Leica DSX is so intriguing. It produces visualizations that are easy for anyone to read and interpret.

“This solves a real customer problem,” said Katy Broder, president of Hexagon’s Construction Tools Division. “There are strikes every day, some with fatalities.”

The Leica DSX can help prevent those strikes. And it produces data fast. After an operator walks the grid with the radar sled, the visualization is available immediately. “You don't have to be trained on how to interpret the results because they’re really that simple,” said Broder.

The Leica DSX won’t completely displace other utility locating technologies, and it might not be especially interesting for utility surveying companies that already own more sophisticated GPR solutions. (Some of those solutions are equipped with multiple antennas and can scan at multiple depths, while the Leica DSX’s single antenna is optimized for scanning to a depth of about 2 meters.) But it’s a tool construction companies can use to do their own scans rather than dig blind or wait three days for results.

GPR isn’t the only tool in the box when it comes to underground utility detection (and it’s not great in certain soil types, such as clay). It’s often used in conjunction with other technologies to paint a complete picture of what’s under the ground. Acoustic detection tools are sometimes used to map underground plastic pipes, for example.

Another common approach is electromagnetic locating, which can be done either actively or passively. With active detection, an electromagnetic signal is transmitted though the conductive material. To map water pipes, the signal is often applied directly to the pipe at a rise or hydrant. Likewise, for mapping electrical lines and phone lines, the equipment is connected directly to a transformer or meter box.

“Typically, we use EM first,” said Brian Holder, president of Utility Locator, LLC. “When you apply a signal, you know what you’re applying it to. GPR can find things you didn’t know were there, but you don’t necessarily know what they are.”

For passive detection, operators use frequency locating equipment to look for electromagnetic energy being generated by utility lines like electrical, phone and fiber optic bundles. Passive detection is often not as accurate or reliable as tapping directly into a known surface point like a hydrant or transformer, and neither electromagnetic approach is as accurate as GPR.

The (subsurface) bottom line: Look before you dig, no matter how you do it. If the new ground penetrating radar solution inspires more companies to do that, it could end up saving lives.

Dave Johnson is a Los Angeles-based freelance writer who writes about all aspects of business and technology since before there was an internet.